24Wx32L Garage Build

I was going to suggest having the width more than the depth to help with opening doors of the cars, but I see the footer is already in.

Mine is 30 wide by 26 deep, and I still can't open both doors on both cars.

You also may wish to consider a 10' wide door vs 9'.

I went with 10' and I'm glad I did. It's MUCH easier to walk in through the roll up door especially if you are carrying something, and not worry about if it will fit, or bumping the car. Plus, if you have any turning involved near the entrance, a wider door is more forgiving of entry angle.